Plasma treatment device and plasma treatment method

ABSTRACT

Uniformity of a plasma process on a surface of a substrate is to be improved. In a plasma processing apparatus that processes a substrate by generating plasma from a processing gas introduced in a processing container, a ratio between an introducing amount of the processing gas introduced to a center portion of the substrate received in the processing container and an introducing amount of the processing gas introduced to a peripheral portion of the substrate received in the processing container is changed during a plasma process. Accordingly, a variation in an etching rate or the like between the center portion and the peripheral portion of the substrate may be reduced. Therefore, uniformity of the plasma process on the surface of the substrate is improved.

TECHNICAL FIELD

The present invention relates to a plasma processing apparatus and aplasma processing method used for manufacturing semiconductors.

BACKGROUND ART

Conventionally, in field of manufacturing semiconductor devices, methodsof performing a process, such as an etching process or a film-formingprocess, by using plasma have been adopted. As one of the methods, aradial line slot antenna (RLSA) type plasma processing apparatus thatgenerates plasma by propagating microwaves from a slot formed in aradial line slot plate into a processing container is well known (forexample, refer to Patent Document 1). An RLSA type plasma processingapparatus has an advantage of performing a plasma process on alarge-sized semiconductor wafer evenly and rapidly, because plasma oflow electron temperature may be evenly generated at a high density. Asan example of the plasma process, a process of etching of a substratesurface performed by using an HBr gas is well known. As another exampleof the plasma process, a process of etching an SiN film formed on asurface of a substrate by using a processing gas including a CF₄ gas anda CHF₃ gas is well known.

In an RLSA type plasma processing apparatus, microwaves are propagatedinside a processing container via a dielectric disposed on a ceilingsurface of the processing container. A processing gas introduced in theprocessing container becomes plasma due to energy of the microwaves, anda surface of a substrate is processed. In general, an introduction unitfor introducing the processing gas into the processing container isdisposed, for example, in a side surface of the processing container.Recently, an introduction unit for introducing the processing gas hasbeen provided in a ceiling surface of the processing container, inaddition to the introduction unit disposed in the side surface of theprocessing container (for example, refer to Patent Document 2).

Patent Document 3 discloses a parallel plate type plasma processingapparatus. In the parallel plate type plasma etching apparatus, a pairof an upper electrode and a lower electrode that are parallel with eachother are provided in a processing container, a radio frequency isapplied to the lower electrode, and at the same time, a substrate isplaced on the lower electrode to be etched. In order to improveuniformity within a surface of the etched substrate, the upper electrodeis divided into a center region for supplying a processing gas to acenter of the substrate, and a peripheral region for supplying theprocessing gas to a peripheral portion of the substrate. In addition, aratio between introducing amounts of the processing gas to the centerportion and the peripheral portion is controlled (Radial distributioncontrol (RDC)).

(Patent Document 1) Japanese Laid-open Patent Publication No. 2009-99807

(Patent Document 2) Japanese Laid-open Patent Publication No.2008-251660

(Patent Document 3) Japanese Laid-open Patent Publication No.2009-117477

DISCLOSURE OF THE INVENTION Technical Problem

Here, in a radial line slot antenna (RLSA) type plasma processingapparatus disclosed in Patent Document 2, improvement of uniformity of aplasma process with respect to a surface of a substrate has beenpromoted by optimizing a ratio between introducing amounts of aprocessing gas from an introduction unit formed on a side surface and anintroducing unit formed in a ceiling surface. In addition, the plasmaprocess has been performed while maintaining the optimized ratio of theintroducing amounts during the process. However, even if the ratio ofthe introducing amounts of the processing gas is optimized, it wasdifficult to perform the plasma process on the surface of the substrateuniformly because etching rates or the like on a center portion of thesubstrate and on a peripheral portion of the substrate are differentfrom each other.

Meanwhile, an accurate control of a critical dimension (CD) of anetching is necessary in order to form super-fine patterns recently.Thus, in processes requiring strict CD control such as processes offorming a mask opening, a spacer, a gate, or the like, a CD value afterthe etching is measured by an optical inspection apparatus in order tocheck various factors contributing to the CD value. However, a method ofeasily controlling the CD value in the etching has not been establishedyet.

In addition, in a parallel plate type plasma processing apparatusdisclosed in Patent Document 3, plasma generated between an upperelectrode and a lower electrode separated in a short distance within 40mm from each other is used, and electron temperature of the plasma ismaintained high throughout from the upper electrode to the lowerelectrode. Also, a common gas and an additive gas are all introduced tothe upper electrode, and thus it may not variously control dissociationof the common gas and the additive gas.

Technical Solution

According to an aspect of the present invention, there is provided aplasma processing apparatus which processes a substrate by generatingplasma from a processing gas introduced into a processing container, theplasma processing apparatus including: a central introduction unit whichintroduces the processing gas onto a center portion of the substratereceived in the processing container; a peripheral introduction unitwhich introduces the processing gas onto a peripheral portion of thesubstrate received in the processing container; a splitter whichvariably adjusts flow rates of the processing gas supplied to thecentral introduction unit and the peripheral introduction unit; and acontroller which controls the splitter, wherein the controller maycontrol the splitter to change a ratio between an introducing amount ofthe processing gas from the central introduction unit and an introducingamount of the processing gas from the peripheral introduction unitduring the plasma process.

According to another aspect of the present invention, there is provideda plasma processing method which processes a substrate by generatingplasma from a processing gas introduced in a processing container, theplasma processing method including changing a ratio between anintroducing amount of the processing gas introduced onto a centerportion of the substrate received in the processing container and anintroducing amount of the processing gas introduced onto a peripheralportion of the substrate received in the processing container, during aplasma process.

According to another aspect of the present invention, there is provideda plasma processing apparatus for etching a substrate by introducing aprocessing gas, in which a plurality of material gases are mixed, into aprocessing container and generating plasma from the processing gas inthe processing container, the plasma processing apparatus including: aplurality of source gas supplying units which supply raw material gasesthat are different from each other; and a controller which controlssupplied amounts of the material gases from the material gas supplyingunits.

According to another aspect of the present invention, there is provideda plasma processing method for etching a substrate by introducing aprocessing gas, in which a plurality of material gases are mixed, into aprocessing container and generating plasma from the processing gas inthe processing container, the plasma processing method includingchanging a mixture ratio of the material gases that are different fromeach other to control a critical dimension (CD).

Advantageous Effects

According to the present invention, a ratio between an introducingamount of a processing gas introduced to a center portion of a substrateand an introducing amount of the processing gas introduced to aperipheral portion of the substrate is changed during a plasma process.Accordingly, a variation in an etching rate or the like between thecenter portion and the peripheral portion of the substrate may bereduced. Therefore, uniformity of the plasma process on the surface ofthe substrate may be improved.

Also, according to the present invention, a ratio of supplying amountsof material gases such as a CF₄ gas or a CHF₃ gas included in theprocessing gas may be changed in order to control a critical dimension(CD) of an etching. In addition, processes for forming a mask opening, aspacer, a gate, or the like, which require strict CD control, may beperformed easily.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal-sectional view schematically showing a plasmaprocessing apparatus according to an embodiment of the presentinvention;

FIG. 2 is a cross-sectional view taken along line X-X of FIG. 1, andshowing a state of a lower surface of a dielectric window;

FIG. 3 is a diagram for describing a state where a processing gas isintroduced into a plasma processing apparatus according to theconventional art;

FIG. 4 is a diagram for describing a state where a processing gas isintroduced into the plasma processing apparatus of FIG. 1;

FIG. 5 is a longitudinal-sectional view schematically showing a plasmaprocessing apparatus according to another embodiment of the presentinvention;

FIG. 6 is a graph showing distribution of etching rates according to afirst comparative example;

FIG. 7 is a graph showing distribution of etching rates according to asecond comparative example;

FIG. 8 is a graph showing distribution of etching rates according to athird comparative example;

FIG. 9 is a graph showing distribution of etching rates according to thefirst embodiment of the present invention;

FIG. 10 is a partially magnified cross-sectional view showing an etchedshape of a SiN film formed on a surface of a wafer according to thesecond embodiment of the present invention;

FIGS. 11A and 11B are partially magnified views showing etched shapes ofan SiN film formed on a surface of a wafer, when an introducing amountof a processing gas on a central portion of the wafer is reduced and anintroducing amount of a processing gas on a peripheral portion of thewafer is increased in plasma processing apparatus according to a thirdembodiment of the present invention; and

FIGS. 12A and 11B are partially magnified views showing etched shapes ofan SiN film formed on a surface of a wafer, when an introducing amountof a processing gas on a central portion of the wafer is increased andan introducing amount of a processing gas on a peripheral portion of thewafer is reduced in the plasma processing apparatus according to thethird embodiment of the present invention.

EXPLANATION ON REFERENCE NUMERALS

W: wafer

1: plasma processing apparatus

2: processing container

3: susceptor

4: external power

5: heater

10: exhaust apparatus

16: dielectric window

20: radial line slot plate

25: dielectric plate

30: coaxial waveguide

31: internal conductor

32: external conductor

35: microwave supply apparatus

36: rectangular waveguide

50, 50′: gas supply source

50 a: Ar gas supplying unit

50 b: HBr gas supplying unit

50 c: O₂ gas supplying unit

50′a: Ar gas supplying unit

50′b: CF₄ gas supplying unit

50′c: CHF₃ gas supplying unit

51: splitter

52, 53: supplying passage

55: central introduction unit

56: peripheral introduction unit

57: injector block

61: injector ring

65: controller

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described withreference to accompanying drawings. In addition, in the presentspecification and drawings, like reference numerals denote likecomponents, and descriptions about the same components are not provided.

As shown in FIG. 1, a plasma processing apparatus 1 according to anembodiment of the present invention includes a processing container 2formed as a cylinder. An upper portion of the processing container 2 isopen, and a bottom portion of the processing container 2 is blocked. Theprocessing container 2 is formed of, for example, aluminum, andelectrically grounded. An inner wall surface of the processing container2 is coated with a protective film, for example, alumna.

A susceptor 3 that is a holding stage on which a substrate, for example,a semiconductor wafer (hereinafter, referred to as a wafer) W, is placedis provided on a bottom portion in the processing container 2. Thesusceptor 3 is formed of, for example, aluminum, and a heater 5generating heat on receiving electric power supplied from an externalpower source 4 is provided in the susceptor 3. The wafer W on thesusceptor 3 may be heated to a predetermined temperature by the heater5.

An exhaust pipe 11 is connected to the bottom portion of the processingcontainer 2 in order to exhaust an inner atmosphere of the processingcontainer 2 by using an exhaust apparatus 10 such as a vacuum pump.

A dielectric window 16 formed of a dielectric material, for example,quartz, is provided on an upper portion of the processing container 2via a sealing material 15 such as an O-ring for ensuring hermeticalproperty. As shown in FIG. 2, the dielectric window 16 is formedapproximately as a disc. The dielectric window 16 may be formed ofanother dielectric material, for example, ceramics such as Al₂O₃ or AlN,instead of quartz.

A slot plate of a flat plate type, for example, a radial line slot plate20 formed as a disc, is provided on an upper portion of the dielectricwindow 16. The radial line slot plate 20 is formed of a thin copper discthat is plated or coated with a conductive material, for example, Ag orAu. A plurality of slots 21 are arranged in the radial line slot plate20 in a plurality of concentric circle shape.

A dielectric plate 25 for reducing wavelength of a microwave is disposedon an upper surface of the radial line slot plate 20. The dielectricplate 25 is formed of a dielectric material, for example, Al₂O₃. Insteadof Al₂O₃, another dielectric material, for example, ceramics such asquartz or AlN, may be used to form the dielectric plate 25. Thedielectric plate 25 is covered by a conductive cover 26. A heat mediumpath 27 of a circular loop type is formed in the cover 26, and the cover26 and the dielectric window 16 are maintained at a predeterminedtemperature by a heat medium flowing in the heat medium path 27.

A coaxial waveguide 30 is connected to a center portion of the cover 26.The coaxial waveguide 30 consists of an internal conductor 31 and anexternal conductor 32. The internal conductor 31 is connected to anupper center portion of the radial line slot plate 20 that is describedabove after penetrating through a center of the dielectric plate 25. Theplurality of slots 21 formed in the radial line slot plate 20 arearranged in a plurality of circumferences that are all formed based onthe internal conductor 31 as a center.

A microwave supply apparatus 35 is connected to the coaxial waveguide 30via a rectangular waveguide 36 and a mode converter 37. A microwavehaving a frequency of, for example, 2.45 GHz, generated by the microwavesupply apparatus 35 is irradiated to the dielectric window 16 via therectangular waveguide 36, the mode converter 37, the coaxial waveguide30, the dielectric plate 25, and the radial line slot plate 20. Inaddition, an electric field is generated on a lower surface of thedielectric window 16 by the microwave, and then plasma is generated inthe processing container 2.

A lower end 40 of the internal conductor 31 that is connected to theradial line slot plate 20 is formed as a circular truncated cone. Asdescribed above, since the lower end 40 of the internal conductor 31 isformed as the circular truncated cone, the microwaves may be propagatedefficiently from the coaxial waveguide 30 toward the dielectric plate 25and the radial line slot plate 20.

The microwave plasma generated by the above structure is characterizedin that plasma having a relatively high electron temperature of about afew eV and generated right under the dielectric window 16 (referred toas plasma excitation region) is diffused, and the plasma becomes to havea relatively low electron temperature of about 1 to 2 eV right above thewafer W (plasma diffusion region). That is, unlike the plasma generatedin the parallel plate type plasma processing apparatus or the like,distribution of the electron temperature of the plasma is accurately setas a distance function from the dielectric window 16. In more detail,according to a distance function from a portion right under thedielectric window 16, the electron temperature of about a few eV toabout 10 eV right under the dielectric window 16 is attenuated to about1 to 2 eV on the wafer W. The process of the wafer W is performed on aregion where the electron temperature of the plasma is low (plasmadiffusion region), and thus a large damage such as a recess in the waferW does not occur. When a processing gas is introduced into a regionwhere the electron temperature of the plasma is high (plasma excitationregion), the processing gas is easily excited and dissociated.Meanwhile, when the processing gas is introduced into the region wherethe electron temperature of the plasma is low (plasma diffusion region),a degree of dissociating the processing gas may be lower than thatsupplied around the plasma excitation region.

The processing gas supplied from a gas supply source 50 is split by asplitter 51, and introduced into the processing container 2 via twosupplying passages 52 and 53. In the plasma processing apparatus 1according to the present embodiment, the gas supply source 50 includesan Ar gas supply unit 50 a supplying an Ar gas, an HBr gas supply unit50 b supplying an HBr gas, and an O₂ gas supply unit 50 c supplying anO₂ gas. A mixture gas of the Ar gas, the HBr gas, and the O₂ gassupplied from the Ar gas supply unit 50 a, the HBr gas supply unit 50 b,and the O₂ gas supply unit 50 c is introduced into the processingcontainer 2 as the processing gas.

A central introduction unit 55 for introducing the processing gas to acenter portion of the wafer W is provided on a ceiling surface of theprocessing container 2. A peripheral introduction unit 56 forintroducing the processing gas to a peripheral portion of the wafer W isprovided on an inner side surface of the processing container 2. Thecentral introduction unit 55 is disposed at a center of the ceilingsurface of the processing container 2. One side of supply passage 52that penetrates through the internal conductor 31 of the coaxialwaveguide 30 is connected to the central introduction unit 55.

An injector block 57 for introducing the processing gas in theprocessing container 2 is attached to the central introduction unit 55.The injector block 57 is formed of, for example, a conductive materialsuch as aluminum, and is electrically grounded. The injector block 57 isformed as a disc, and a plurality of gas ejection holes 58 penetratingthe injector block 57 in an up-and-down direction thereof are providedin the injector block 57. The injector block 57 may be coated with, forexample, alumina or Yttria.

As shown in FIG. 2, the injector block 57 is held at a space portion 59formed as a cylinder at a center of the dielectric window 16. A gasreservoir unit 60 formed as a cylinder is formed between a lower surfaceof the internal conductor 31 of the coaxial waveguide 30 and an uppersurface of the injector block 57 with an appropriate distance. Theprocessing gas supplied from the supplying passage 52 that penetratesthrough the internal conductor 31 to the gas reservoir unit 60 isdispersed in the gas reservoir unit 60, and after that, is introducedinto an upper portion of the center of the wafer W in the processingcontainer 2 via the plurality of gas ejection holes 58 formed in theinjector block 57.

The peripheral introduction unit 56 includes an injector ring 61 formedas a ring that surrounds an upper portion of the wafer W placed on thesusceptor 3. The injector ring 61 is hollow, and the processing gas issupplied in the injector ring 61 through the supplying passage 53 thatpenetrates through the side surface of the processing container 2. Aplurality of openings 62 are provided in an inner side surface of theinjector ring 61 at constant intervals. The processing gas supplied intothe injector ring 61 from the supplying passage 53 that penetratesthrough the side surface of the processing container 2 is dispersed inthe injector ring 61, and after that, is introduced to a peripheralupper portion of the wafer W in the processing container 2 via theplurality of openings 62 provided in the inner side surface of theinjector ring 61. Otherwise, the injector ring 61 may not be provided.For example, supplying nozzles of the processing gas may be provided inthe inner side surface of the processing container 2 at constantintervals.

The splitter 51, and the Ar gas supplying unit 50 a, the HBr gassupplying unit 50 b, and the O₂ gas supplying unit 50 c of the gassupply source 50 are controlled by the controller 65. A ratio of the Argas supplied from the Ar gas supplying unit 50 a to the splitter 51, aratio of the HBr gas supplied from the HBr gas supplying unit 50 b tothe splitter 51, and a ratio of the O₂ gas supplied from the O₂ gassupplying unit 50 c to the splitter 51 are determined by the control ofthe controller 64. Accordingly, composition of the processing gasintroduced into the processing container 2 is determined. According tothe control of the controller 65, flow rates of the processing gasesthat are split by the splitter 51 toward the two supplying passages 52and 53 to be supplied to the central introduction unit 55 and theperipheral introduction unit 56 are determined. Therefore, a ratiobetween introducing amounts of the processing gas supplied from thecentral introduction unit 55 and the peripheral introduction unit 56 tothe processing container 2 is determined.

When the processing gas is introduced from the central introduction unit55 to the portion right under the dielectric window 16, it is easy todissociate the processing gas since the electron temperature of theplasma is high. On the other hand, when the processing gas is introducedfrom the peripheral introduction unit 56 that is relatively far from thedielectric window 16, the dissociation of the processing gas may berestrained because the electron temperature of the plasma is low.Therefore, in order to obtain a desired level of dissociation state ofthe processing gas, the dissociation state may be easily controlled byadjusting an amount of the processing gas supplied from the centralintroduction unit 55 and an amount of the processing gas supplied fromthe peripheral introduction unit 56.

Next, operations of the plasma processing apparatus 1 of the abovestructure according to the embodiment of the present invention will bedescribed. In the plasma processing apparatus 1 of the presentembodiment, an example in which a poly-Si film on the surface of thewafer W is etched by using an example of the processing gas includingthe HBr gas will be described as follows.

As shown in FIG. 1, in the plasma processing apparatus 1 according tothe present embodiment, the wafer W is carried into the processingcontainer 2, and placed on the susceptor 3. The processing container 2is decompressed by an exhaust performed through the exhaust pipe 11. Inaddition, a processing gas including the Ar gas, the HBr gas, and the O₂gas is introduced from the gas supply source 50. In this case, a ratioof the Ar gas supplied from the Ar gas supplying unit 50 a to thesplitter 51, a ratio of the HBr gas supplied from the HBr gas supplyingunit 50 b to the splitter 51, and a ratio of the O₂ gas supplied fromthe O₂ gas supplying unit 50 c to the splitter 51 are determined by thecontrol of the controller 65, and accordingly, composition of theprocessing gas is determined. In addition, the processing gas having apredetermined composition mixed in the splitter 51 is introduced intothe processing container 2.

The introduction of the processing gas into the processing container 2is performed simultaneously from the central introduction unit 55provided on the ceiling surface of the processing container 2 and fromthe peripheral introduction unit 56 provided on the inner side surfaceof the processing container 2, and thus the processing gas is introducedto both of the center portion and the peripheral portion of the wafer W.A ratio between the introducing amounts of the processing gas from thecentral introduction unit 55 and the processing gas from the peripheralintroduction unit 56 is determined by the controller 65 such that theetching process may be performed uniformly on the entire surface of thewafer W. The controller 65 controls the splitter 51, and the processinggas is introduced into the processing container 2 from the centralintroduction unit 55 and the peripheral introduction unit 56 accordingto the determined ratio.

In addition, when the microwave supply apparatus 35 operates, anelectric field is generated on a lower surface of the dielectric window16, and then the processing gas becomes plasma. Also, the poly-Si filmon the surface of the wafer W is etched by active species generated atthis time. After performing the etching process for a predeterminedtime, the operation of the microwave supply apparatus 35 and the supplyof the processing gas into the processing container 2 are stopped, andthe wafer W is carried out of the processing container 2, then a seriesof plasma etching processes is finished.

However, in the plasma processing apparatus 1 described above, in orderto improve etching uniformity of the poly-Si film on the surface of thewafer W, conventionally a ratio between the introducing amount of theprocessing gas from the central introduction unit 55 and the introducingamount of the processing gas from the peripheral introduction unit 56 isoptimized. The controller 65 conventionally controls the ratio betweenthe introducing amounts split by the splitter 51 to be constant duringthe plasma process. However, even when the ratio between the introducingamounts of the processing gas from the central introduction unit 55 andfrom the peripheral introduction unit 56 is optimized at high accuracy,the etching rates at the center portion and the peripheral portion onthe surface of the wafer W are greatly different from each other, andthus, it is difficult to perform the etching process uniformly.

Here, causes of the difference between the etching rates on the centerportion and the peripheral portion of the surface of the wafer W whenthe processing gases are introduced from the central introduction unit55 and the peripheral introduction unit 56 are examined. As shown inFIG. 3, conventionally, a ratio Q/R between an introducing amount Q of aprocessing gas G1 introduced from the central introduction unit 55 andan introducing amount R of a processing gas G2 introduced from theperipheral introduction unit 56 is constantly maintained by the controlof the controller 65 during the plasma process. Thus, the processing gasG1 introduced from the central introduction unit 55 and the processinggas G2 introduced from the peripheral introduction unit 56 alwayscollide with each other at a constant position P on the surface of thewafer W that is placed on the susceptor 3. Accordingly, settling down ofthe processing gas G1 and the processing gas G2 at the position P isexpected. In addition, it is estimated that the settling down of theprocessing gas G1 and the processing gas G2 at the constant position Pbecomes the cause of the difference between the etching rates on thecenter portion and the peripheral portion of the surface of the wafer W.

Therefore, the present inventors tried to reduce the difference betweenthe etching rates on the center portion and the peripheral portion ofthe surface of the wafer W by moving the position at which theprocessing gas is settled down during the plasma process by the controlof the controller 65 on the surface of the wafer W. As denoted by solidlines in FIG. 4, the processing gas G1 is introduced from the centralprocessing unit 55 at an introducing amount Q1 first, and the processinggas G2 is introduced from the peripheral introduction unit 56 at anintroducing amount R1 (that is, the introducing amount ratio split bythe splitter 51 is controlled at Q1/R1 by the controller 65). Here, theprocessing gas G1 introduced from the central introduction unit 55 andthe processing gas G2 introduced from the peripheral introduction unit56 collide with each other at a position P1 on the surface of the waferW placed on the susceptor 3.

Next, during continuing the plasma process, as denoted by dash-dot linesin FIG. 4, the processing gas G1 is introduced from the centralintroduction unit 55 at an introducing amount Q2 (Q2<Q1), and theprocessing gas G2 is introduced from the peripheral introduction unit 56at an introducing amount R2 (R2>R1) (that is, the ratio between theintroducing amounts split by the splitter 51 is controlled to be Q2/R2by the controller 65). Here, the processing gas G1 introduced from thecentral introduction unit 55 and the processing gas G2 introduced fromthe peripheral introduction unit 56 collide with each other at aposition P2 that is closer to the center of the wafer W than theposition P1, on the surface of the wafer W placed on the susceptor 3.

In addition, during continuing the plasma process, the ratio between theintroducing amounts split by the splitter 51 is controlled alternatelybetween Q1/R1 and Q2/R2 by the controller 65, and thus a state where theprocessing gas G1 is introduced from the central introduction unit 55 atthe introducing amount Q1 and the processing gas G2 is introduced fromthe peripheral introduction unit 56 at the introducing amount R1 (Q1/R1)and a state where the processing gas G1 is introduced from the centralintroduction unit 55 at the introducing amount Q2 and the processing gasG2 is introduced from the peripheral introduction unit 56 at theintroducing amount R2 (Q2/R2) are alternately switched. As describedabove, by alternately changing the states of the introducing amountratio Q1/R1 and Q2/R2, the position where the processing gas G1 and theprocessing gas G2 collide with each other on the surface of the wafer Wmay be alternately moved between the position P1 and the position P2.

From above result of the experiment, the present inventors obtainedknowledge that the difference between the etching rates on the centerportion and the peripheral portion of the surface of the wafer W may bereduced and thus uniform etching may be performed, by controlling theratio between the introducing amounts split by the splitter 51 to bechanged during the plasma process by using the controller 65, andchanging the ratio between the introducing amount of the processing gasG1 from the central introduction unit 55 and the introducing amount ofthe processing gas G2 from the peripheral introduction unit 56 duringthe plasma process. Also, the experiment through which the presentinventors obtain the above knowledge will be described later.

Therefore, according to the plasma processing apparatus 1 of the presentembodiment, the ratio between the introducing amounts split by thesplitter 51 is changed during the plasma process by the controller 65,and thus the uniformity of the plasma process on the surface of thewafer W may be improved. Accordingly, semiconductor devices havingexcellent performances may be manufactured.

Next, a plasma processing apparatus 1′ according to another embodimentof the present invention will be described. As shown in FIG. 5, in theplasma processing apparatus 1′ according to the present embodiment, agas supply source 50′ includes an Ar gas supplying unit 50′a supplyingan Ar gas, a CF₄ gas supplying unit 50′b supplying a CF₄ gas, and a CHF₃gas supplying unit 50′c supplying a CHF₃ gas. A mixture gas of the Argas, the CF₄ gas, and the CHF₃ gas supplied from the Ar gas supplyingunit 50′a, the CF₄ gas supplying unit 50′b, and the CHF₃ gas supplyingunit 50′c is supplied into the processing container 2 as a processinggas. The plasma processing apparatus 1′ of the present embodiment issubstantially the same as the plasma processing apparatus 1 of theprevious embodiment, except for that the kinds of the processing gasesin the gas supply source 50 and in the gas supply source 50′ aredifferent from each other. Thus, descriptions about other componentsexcept for the gas supply source 50′ are not provided here.

Next, operations of the plasma processing apparatus 1′ of the presentembodiment will be described. In addition, in the plasma processingapparatus 1′ of the present embodiment, an example of etching an SiNfilm formed on the surface of the wafer W by using a processing gasincluding the CF₄ and the CHF₃ gas will be described as an example ofthe plasma process.

As shown in FIG. 5, in the plasma processing apparatus 1′ of the presentembodiment, the wafer W is carried into the processing container 2, andplaced on the susceptor 3. In addition, inside of the processingcontainer 2 is decompressed by the exhaustion of the exhaust pipe 11.Also, the processing gas including the Ar gas, the CF₄ gas, and the CHF₃gas is introduced from the gas supply source 50′. In this case, a ratioof the Ar gas supplied from the Ar gas supplying unit 50′a to thesplitter 41, a ratio of the CF₄ gas supplied from the CF₄ gas supplyingunit 50′b to the splitter 51, and a ratio of the CHF₃ supplying unit50′c to the splitter 51 are determined by the control of the controller65 so as to determine a mixture ratio of each of material gases (Ar gas,CF₄ gas, and CHF₃ gas) in the processing gas. In addition, theprocessing gas mixed in the splitter 51 is introduced into theprocessing container 2.

The introducing of the processing gas into the processing container 2 isperformed simultaneously from the central introduction unit 55 providedon the ceiling surface of the processing container 2 and the peripheralintroduction unit 56 provided on the inner side surface of theprocessing container 2, and thus the processing gas is introduced toboth of the center portion and the peripheral portion of the wafer W. Aratio between the introducing amount of the processing gas from thecentral introduction unit 55 and the introducing amount of theprocessing gas from the peripheral introduction unit 56 is determinedwhen the controller 65 controls the splitter 51, and the ratio betweenthe introducing amounts split by the splitter 51 is adjusted such thatthe etching process may be performed throughout the entire surface ofthe wafer W uniformly.

In addition, an electric field is generated on the lower surface of thedielectric window 16 by the operation of the microwave supply apparatus35, and then the processing gas becomes plasma. The SiN film on thesurface of the wafer W is etched by active species generated at thistime. After performing the etching process for a predetermined time, theoperation of the microwave supply apparatus 35 and the supply of theprocessing gas into the processing container 2 are stopped, and thewafer W is carried out of the processing container 2. Then, a series ofplasma etching processes is finished.

However, in the plasma processing apparatus 1′ of the present embodimentdescribed above, it is required to accurately control a criticaldimension (CD) of the etching in order to form recent ultra-finepatterns. Meanwhile, according to the knowledge of the presentinventors, when the mixture ratio of the CF₄ gas and the CHF₃ gas in theprocessing gas that is introduced to the processing container 2 andbecomes plasma is changed, the CD of the SiN film on the surface of thewafer W, which is etched, is changed. Also, an experiment through whichthe present inventor obtained the knowledge will be described later.

Thus, in the plasma processing apparatus 1′ of the present embodiment, asupplying amount of the CF₄ gas supplied from the CF₄ gas supplying unit50′b to the splitter 51, and a supplying amount of the CHF₃ gas suppliedfrom the CHF₃ gas supplying unit 50′c to the splitter 51 are adjusted bythe controller 65 to change the mixture ratio of the CF₄ gas and theCHF₃ gas in the processing gas, and thus the CD of the SiN film on thesurface of the wafer W is controlled. Thus, the CD of the SiN film onthe surface of the wafer W is easily controlled. Accordingly, theetching processes requiring a strict CD control such as processes offorming a mask opening, a spacer, or a gate may be easily performed.

In the plasma processing apparatus 1′ of the present embodiment, thecontroller 65 may control the ratio between the introducing amountssplit by the splitter 51 to be changed during the plasma process, andthe ratio between the introducing amount of the processing gas G1 fromthe central introduction unit 55 and the introducing amount of theprocessing gas G2 from the peripheral introduction unit 56 is changedduring the plasma process. Thus, the difference between the etchingrates at the center portion and the peripheral portion on to the surfaceof the wafer W is reduced, and the etching may be performed uniformly.Accordingly, semiconductor devices having excellent performances may bemanufactured.

As described above, examples of the embodiments of the present inventionare described; however, the present invention is not limited to theabove examples. Those who skilled in the art would appreciate that anymodified examples that do not depart from the spirit and technical scopeof the present invention are included in the scope of the presentinvention.

In the above described embodiments, the present invention is applied tothe plasma processing apparatus 1 or 1′ performing the etching process;however, the present invention may be also applied to a plasmaprocessing apparatus performing other substrate processes, such as afilm-forming process, besides the etching process.

In the above described embodiments, an example where the poly-Si film onthe surface of the wafer W is etched by using the processing gasincluding the HBr gas and an example where the SiN film on the surfaceof the wafer W is etched by using the processing gas including theCF_(4 gas) and the CHF₃ gas as source gases are described; however, thepresent invention may be applied to an etching process using anotherprocessing gas including other source gases besides the HBr gas, the CF₄gas, and the CHF₂ gas. In addition, an object to be etched is notlimited to the poly-Si film and the SiN film. In addition, the presentinvention is not limited to a plasma etching apparatus of an RLSA type,and may be applied to another ECR type plasma etching apparatus. Inaddition, a substrate processed in the plasma processing apparatus ofthe present invention may be any of a semiconductor wafer, an organicelectroluminescence (EL) substrate, and a substrate for a flat paneldisplay (FPD).

Embodiment 1

A difference between the etching rates at the center portion and theperipheral portion on the surface of the wafer W was considered withrespect to the ratio between the introducing amounts split by thesplitter 51. In addition, a Si wafer having a diameter of 300 mm wasused, and a poly-Si film formed on the surface of the wafer W wasetched.

Comparative Examples 1 through 3

Tables 1 through 3 respectively show processing conditions incomparative examples to 1 through 3. In the comparative examples 1through 3, the ratio between the introducing amounts split by thesplitter 51 was constantly maintained during the plasma process, and anetching process Poly for removing the poly-Si film was performed for 30seconds. During the etching process Poly, a ratio between theintroducing amount of the processing gas G1 from the centralintroduction unit 55 and the introducing amount of the processing gas G2from the peripheral introduction unit 56 was maintained at 25/75 in thecomparative example 1, at 32/68 in the comparative example 2, and at40/60 in the comparative example 3. In addition, when initiating theetching process, a breakthrough process BT for removing an oxide filmformed on the surface of the wafer W was performed for 7 seconds, andafter that, the etching process Poly was performed.

TABLE 1 Introducing Ar HBr O₂ Pressure amount ratio MW RF Time BT  250sccm 150 sccm  10 mTorr 40/60 2500 MHz 150 MHz  7 sec Poly 1000 sccm 600sccm 8 sccm 100 mTorr 25/75 2500 MHz 200 MHz 30 sec

TABLE 2 Introducing Ar HBr O₂ Pressure amount ratio MW RF Time BT  250sccm 150 sccm  10 mTorr 40/60 2500 MHz 150 MHz  7 sec Poly 1000 sccm 600sccm 8 sccm 100 mTorr 32/68 2500 MHz 200 MHz 30 sec

TABLE 3 Introducing Ar HBr O₂ Pressure amount ratio MW RF Time BT  250sccm 150 sccm  10 mTorr 40/60 2500 MHz 150 MHz  7 sec Poly 1000 sccm 600sccm 8 sccm 100 mTorr 40/60 2500 MHz 200 MHz 30 sec

Embodiment 1

Table 4 shows processing conditions of the embodiment 1. In theembodiment 1, when initiating the etching process, a breakthroughprocess BT was performed for 7 seconds in order to remove an oxide filmformed on the surface of the wafer W. After that, an etching processPoly1 for removing a poly-Si film by introducing the processing gas G1from the central introduction unit 55 and the processing gas G2 from theperipheral introduction unit to G2 at a ratio of 25/75 for threeseconds, and an etching process Poly2 for removing the poly-Si film byintroducing the processing gas G1 from the central introduction unit 55and the processing gas G2 from the peripheral introduction unit 56 at aratio of 40/60 for three seconds were alternately and repeatedlyperformed five times.

TABLE 4 Introducing Ar HBr O₂ pressure amount ratio MW RF Time BT  250sccm 150 sccm  10 mTorr 40/60 2500 MHz 150 MHz 7 sec Poly1 1000 sccm 600sccm 8 sccm 100 mTorr 25/75 2500 MHz 200 MHz 3 sec Poly2 1000 sccm 600sccm 8 sccm 100 mTorr 40/60 2500 MHz 200 MHz 3 sec Poly1 1000 sccm 600sccm 8 sccm 100 mTorr 25/75 2500 MHz 200 MHz 3 sec Poly2 1000 sccm 600sccm 8 sccm 100 mTorr 40/60 2500 MHz 200 MHz 3 sec Poly1 1000 sccm 600sccm 8 sccm 100 mTorr 25/75 2500 MHz 200 MHz 3 sec Poly2 1000 sccm 600sccm 8 sccm 100 mTorr 40/60 2500 MHz 200 MHz 3 sec Poly1 1000 sccm 600sccm 8 sccm 100 mTorr 25/75 2500 MHz 200 MHz 3 sec Poly2 1000 sccm 600sccm 8 sccm 100 mTorr 40/60 2500 MHz 200 MHz 3 sec Poly1 1000 sccm 600sccm 8 sccm 100 mTorr 25/75 2500 MHz 200 MHz 3 sec Poly2 1000 sccm 600sccm 8 sccm 100 mTorr 40/60 2500 MHz 200 MHz 3 sec

FIGS. 6 through 9 respectively show results of the comparative examples1 through 3, and the embodiment 1. In FIGS. 6 through 9, transverse axesdenote locations on the surface of the wafer W (0 denotes the center),and longitudinal axes denote etching rate (ER).

Comparative Example 1

As shown in FIG. 6, in the comparative example 1, the etching rate ERwas greater at the peripheral portion of the wafer W, and was reduced atthe center portion of the wafer W. Uniformity of the etching rate ER(average value of the etching rate ER±variation amount of the etchingrate ER) was 121.0 nm/min±43.7%.

Comparative Example 2

As shown in FIG. 7, in the comparative example 2, the etching rate ERwas greater at the center portion of the wafer W, and was minimizedbetween the center portion and the peripheral portion of the wafer W.Uniformity of the etching rate ER (average value of the etching rateER±variation amount of the etching rate ER) was 164.5 nm/min±25.0%.

Comparative Example 3

As shown in FIG. 8, in the comparative example 3, the etching rate ERwas greater at the center portion of the wafer W, and was reduced at theperipheral portion of the wafer W. Uniformity of the etching rate ER(average value of the etching rate ER±variation amount of the etchingrate ER) was 198.2 nm/min±22.6%.

Embodiment 1

As shown in FIG. 9, in the embodiment 1, the etching rate ER wasslightly greater at the peripheral portion of the wafer W; however, theetching rate ER was nearly uniform between the center portion and theperipheral portion of the wafer W. Uniformity of the etching rate ER(average value of the etching rate ER±variation amount of the etchingrate ER) was 148.5 nm/min±18.1%. When comparing with the comparativeexamples 1 through 3, the variation amount of the etching rate ER of theembodiment 1 was the smallest.

Embodiment 2

When a SiN film on the surface of the wafer W is etched by using aprocessing gas including a CF₄ gas and a CHF₃ gas as material gases, arelation between the mixture ratio of the CF₄ gas and the CHF₃ (CF₄gas/CHF₃ gas) and the CD was examined. FIG. 10 shows an etched shape ofthe SiN film on the surface of the wafer W. Table 5 shows the relationbetween the mixture ratio of the CF₄ gas and the CHF₃ gas (CF₄ gas/CH F₃gas) and the CD.

TABLE 5 CF₄ gas/CHF₃ gas (sccm/sccm) 120/240 150/210 180/180 240/120 CD(nm) 63 60 50 49

In the present embodiment, when the mixture ratio of the CF₄ gas and theCHF₃ gas (CF₄/CHF₃) is increased, the CD becomes smaller. From theresult of the embodiment 2, it may be acknowledged that the CD duringthe etching process of the SiN film may be controlled by changing themixture ratio of the CF₄ gas and the CHF₃ gas in the processing gas.

Embodiment 3

Next, influence of the ratio between the introducing amount of theprocessing gas (processing gas including the CF₄ gas and the CHF₃ gas asmaterial gases) introduced at the center portion of the wafer W and theintroducing amount of the processing gas introduced at the peripheralportion of the wafer W was examined. In addition, the mixture ratio(CF₄/CHF₃) of the processing gas introduced on the center portion of thewafer W and the processing gas introduced on the peripheral portion ofthe wafer W were the same as each other. As shown in FIG. 11, when theintroducing amount of the processing gas onto the center portion of thewafer is less and the introducing amount of the processing gas onto theperipheral portion of the wafer is greater, the etched shape of the SiNfilm of the surface of the wafer at the center portion of the wafer hastapered shape in which a width of the SiN film is wider as the sides getnear to a bottom portion thereof (a), and the SiN film of the surface ofthe wafer on the peripheral portion of the wafer was etched so as tohave nearly perpendicular sides (b). Meanwhile, as shown in FIG. 12,when the introducing amount of the processing gas onto the centerportion of the wafer is greater and the introducing amount of theprocessing gas onto the peripheral portion of the wafer is less, the SiNfilm of the surface of the wafer on the center portion of the wafer wasetched so as to have nearly perpendicular sides (a), and the SiN film ofthe surface of the wafer on the peripheral portion of the wafer wasetched to have tapered shape in which a width of the SiN film is wideras the sides get near to the bottom portion thereof (b).

From the results of the embodiments 2 and 3, it is acknowledged that theCD in the etching process of the SiN film may be controlled by changingthe mixture ratio of the CF₄ gas and the CHF₃ gas in the processing gas,and the ratio between the introducing amounts of the processing gasintroduced onto the center portion of the wafer and the processing gasintroduced onto the peripheral portion of the wafer, thereby controllingthe etched shape of the SiN film.

INDUSTRIAL APPLICABILITY

The present invention is advantageous in, for example, semiconductormanufacturing field.

1. A plasma processing apparatus which processes a substrate bygenerating plasma from a processing gas introduced in a processingcontainer, the plasma processing apparatus comprising: a centralintroduction unit which introduces the processing gas onto a centerportion of the substrate received in the processing container; aperipheral introduction unit which introduces the processing gas onto aperipheral portion of the substrate received in the processingcontainer; a splitter which variably adjusts flow rates of theprocessing gas supplied to the central introduction unit and theperipheral introduction unit; and a controller which controls thesplitter, wherein the controller controls the splitter to change a ratiobetween an introducing amount of the processing gas from the centralintroduction unit and an introducing amount of the processing gas fromthe peripheral introduction unit during the plasma process.
 2. Theplasma processing apparatus of claim 1, wherein the controller controlsthe splitter to alternately switch the ratio between the introducingamount of the processing gas from the central introduction unit and theintroducing amount of the processing gas from the peripheralintroduction unit into a first introducing amount ratio and a secondintroducing amount ratio that is different from the first introducingamount ratio, during the plasma process.
 3. The plasma processingapparatus of claim 1, wherein the central introduction unit is providedon a ceiling surface of the processing container, and the peripheralintroduction unit is provided on an inner side surface of the processingcontainer.
 4. The plasma processing apparatus of claim 1, wherein theprocessing gas comprises HBr.
 5. A plasma processing method whichprocesses a substrate by generating plasma from a processing gasintroduced into a processing container, the plasma processing methodcomprising changing a ratio between an introducing amount of theprocessing gas introduced onto a center portion of the substratereceived in the processing container and an introducing amount of theprocessing gas introduced onto a peripheral portion of the substratereceived in the processing container, during a plasma process.
 6. Theplasma processing method of claim 5, wherein the ratio between theintroducing amount of the processing gas from the central introductionunit and the introducing amount of the processing gas from theperipheral introduction unit is alternately switched into a firstintroducing amount ratio and a second introducing amount ratio that isdifferent from the first introducing amount ratio.
 7. The plasmaprocessing method of claim 5, wherein the processing gas comprises HBr.8. A plasma etching apparatus for etching a substrate by introducing aprocessing gas, in which a plurality of material gases are mixed, into aprocessing container and generating plasma from the processing gas inthe processing container, the plasma etching apparatus comprising: aplurality of material gas supplying units which supply material gasesthat are different from each other; and a controller which controlssupplied amounts of the material gases from the material gas supplyingunits.
 9. The plasma etching apparatus of claim 8, further comprising: acentral introduction unit which introduces the processing gas onto acenter portion of the substrate received in the processing container; aperipheral introduction unit which introduces the processing gas onto aperipheral portion of the substrate received in the processingcontainer; and a splitter which variably adjusts flow rates of theprocessing gas supplied to the central introduction unit and theperipheral introduction unit, wherein the controller controls thesplitter to change a ratio between an introducing amount of theprocessing gas from the central introduction unit and an introducingamount of the processing gas from the peripheral introduction unitduring a plasma etching process.
 10. The plasma etching apparatus ofclaim 8, wherein the plurality of material gas supplying units comprise:a CF₄ gas supplying unit which supplies a CF₄ gas; and a CHF₃ gassupplying unit which supplies a CHF₃ gas, wherein the controllercontrols a supplying amount of the CF₄ gas from the CF₄ gas supplyingunit and a supplying amount of the CHF₃ gas from the CHF₃ gas supplyingunit.
 11. A plasma etching method for etching a substrate by introducinga processing gas, in which a plurality of material gases are mixed, intoa processing container and generating plasma from the processing gas inthe processing container, the plasma etching method comprising changinga mixture ratio of the material gases that are different from each otherto control a critical dimension (CD).
 12. The plasma etching method ofclaim 11, wherein a ratio between an introducing amount of theprocessing gas introduced on a center portion of the substrate and anintroducing amount of the processing gas introduced on a peripheralportion of the substrate is changed during a plasma etching process. 13.The plasma etching method of claim 11, wherein the plurality of materialgases comprise a CF₄ gas and a CHF₃ gas, and a supplying amount of theCF₄ gas and a supplying amount of the CHF₃ gas are controlled.